Problem: Khan.scratchpad.disable(); To move up to the maestro level in his piano school, Kevin needs to master at least $91$ songs. Kevin has already mastered $31$ songs. If Kevin can master $9$ songs per month, what is the minimum number of months it will take him to move to the maestro level?
Answer: To solve this, let's set up an expression to show how many songs Kevin will have mastered after each month. Number of songs mastered $=$ $ $ Months at school $\times$ Songs mastered per month $+$ Songs already mastered Since Kevin Needs to have at least $91$ songs mastered to move to maestro level, we can set up an inequality to find the number of months needed. Number of songs mastered $\geq 91$ Months at school $\times$ Songs mastered per month $ +$ Songs already mastered $\geq 91$ We are solving for the months spent at school, so let the number of months be represented by the variable $x$ We can now plug in: $x \cdot 9 + 31 \geq 91$ $ x \cdot 9 \geq 91 - 31 $ $ x \cdot 9 \geq 60 $ $x \geq \dfrac{60}{9} \approx 6.67$ Since we only care about whole months that Kevin has spent working, we round $6.67$ up to $7$ Kevin must work for at least 7 months.